Kismet Turning Radius Gauges

[akstsstjs]

I have recently acquired these.
No instructions, but I have read up on the internet and understand how to use generic ones.
I was expecting the locking pins to lock the turntables in position at zero degrees.
They don't.
They only lock the front to back, sliding horizontal movement of the upper half of the gauges including the turntables, not the turntables themselves.
Are they meant to lock the turntables and are broken?
Am I missing a hidden feature that will lock the turntables?
Were the gauges designed without a lock for the turntables? If, so I don't see how they can work?
Does anyone have personal experience of using these gauges?
Does anyone have a set of Instructions for these gauges?
Any help is much appreciated.

[akstsstjs]

Excellent feedback thanks.
The sideways orientation, sideways sliding motion and sideways locking pins all makes perfect sense.
That just leaves the apparent lack of a locking mechanism for the turntables.

[akstsstjs]

Looking at other brands they all seem to have locking pins to lock the turntables and keep them in place at zero degrees whilst you drive onto them.
The locking pins are then removed so the turntables can be used and rotated.